COMMENTARY

Age-Related Macular Degeneration and Calcium Supplements: Is There a Reason to Change Clinical Practice?

Charles C. Wykoff, MD, PhD

Disclosures

August 14, 2015

In This Article

AMD and Calcium Supplementation: Recent Controversy

Given the considerable prevalence of AMD and widespread calcium supplementation among Americans, a recent exploratory analysis of the relationship between AMD and calcium supplementation has garnered significant attention.[16] Unfortunately, the published conclusion is misleading and has led to unfounded concern and inappropriate consideration of cessation of suitable calcium supplementation among at-risk Americans.

Kakigi and colleagues[16] used the public National Health and Nutrition Examination Survey (NHANES) database from 2007-2008 to investigate the relationship between AMD and self-reported calcium supplementation. The Centers for Disease Control and Prevention (CDC) performs the NHANES annually to assess the health status of the US population. It typically includes an interview questionnaire and physical examination of approximately 5000 participants. In the 2007-2008 NHANES, fundus photographs were also obtained for participants who were 40 years of age or older and were graded for the presence or absence of AMD by trained professionals at the University of Wisconsin.

Of the 3191 participants who were 40 years of age or older, 248 (7.8%) were graded as having AMD: 220 with "early AMD" and 28 with "late AMD." The authors did not define "early" and "late" AMD. Presumably, "late AMD" referred to advanced AMD, defined as either neovascularization or the development of geographic atrophy, but this was not clearly stated. Of these 248 participants with AMD, 146 adults (59%) reported taking calcium supplements. The authors then divided this relatively small sample size into quintiles based on the daily milligrams of calcium supplements consumed as self-reported by the participants. The prevalence of AMD was then assessed within each quintile. Each calcium supplement quintile had 23-44 total patients—small numbers to make substantial population-wide inferences.

As expected with such an epidemiologic study, there were significant differences between the populations with and without AMD. For example, participants with and without AMD were 67.2 and 55.8 years old, respectively, a difference of more than 11 years. Similarly, participants with AMD were significantly more likely to be smokers and reported no alcohol consumption. The authors adjusted for these and at least 14 confounders before reporting an increased prevalence of AMD among participants in the highest quintile of calcium supplement use (more than 800 mg daily) compared with those who did not report consuming calcium supplements (odds ratio of 1.85; associated 95% confidence interval, 1.25-2.75). Only 44 AMD patients reported daily calcium supplementation with more than 800 mg, representing 1.4% of the total population studied.

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